His returns, spanning more than 500 pages and released under political pressure Tuesday, represent an extraordinary financial accounting of one of the wealthiest U.S. presidential candidates in generations, with his annual income topping $20 million.

It remains unclear how the details of Romney's fortune will play among American workers, who on average earn less in a lifetime than Romney paid in taxes in 2010 alone. Meanwhile, the typical taxpayer pays a similar share of his income to Uncle Sam as he does, roughly 15 percent.

Romney's returns — which include a 2011 tax estimate — spilled out new details of his scattered holdings, tax strategies and charitable donations. Romney paid about $3 million in federal income taxes in 2010, having earned more than seven times that from his investments.

The documents quickly became fodder for his opponents, with Democrats chiding the former Massachusetts governor for not disclosing more about his financial history. The White House also weighed in about tax fairness as President Barack Obama prepared for his State of the Union Address.

Romney is hardly the only wealthy American seeking the presidency, though he's on a level all his own.

Republican rival Newt Gingrich, who had publicly pressed him to release his tax information, released his own return for 2010 last week. It revealed that Gingrich earned more than $3.1 million, mostly from $2.5 million paid by his companies, partnerships and investments, and paid just under $1 million in federal tax, a rate of about 31 percent.

Obama and his wife, Michelle, reported income of $1.73 million last year, mostly from the books he's written, and paid $453,770 in federal taxes.

Romney's tax returns showed he continues to profit from Bain Capital, the private equity firm he founded but no longer runs; from a Swiss bank account closed just as he launched his campaign and from new listings of investment funds set up overseas.

Romney had long refused to disclose any federal tax returns, then hinted he would offer a single year's return in April. Yet mounting criticism from his rivals and a hard loss in last week's South Carolina primary forced his hand.

"Governor Romney has paid 100 percent of what he owes," said Benjamin Ginsberg, the campaign's legal counsel. Ginsberg and other advisers said Romney did not use any aggressive tax strategies to help reduce or defer his tax income.

For 2011, Romney will pay about $3.2 million with an effective tax rate of about 15.4 percent, the campaign said. Those returns haven't yet been filed yet with the Internal Revenue Service. In total, he would pay more than $6.2 million in taxes on $45 million in income over the past two years, his campaign said.

Romney had been cast by his GOP opponents as a wealthy businessman who earned lucrative payouts from his investments while Bain slashed jobs in the private sector. Romney concedes that some companies Bain invested in were unsuccessful but says others created large numbers of jobs.

As for his own tax payments, he said in Monday night's debate in Tampa, "I pay all the taxes that are legally required and not a dollar more. ... I don't think you want someone as the candidate for president who pays more taxes than he owes."

He added, "You'll see my income, how much taxes I've paid, how much I've paid to charity."

Romney's 2010 return showed about $4.5 million in itemized deductions, including $1.5 million contributed to the Church of Jesus Christ of Latter-day Saints. Romney's charitable giving is above average, even for someone at his income level, according to IRS data.

Romney's GOP rivals did not immediately comment on his tax disclosures. But House Speaker John Boehner, R-Ohio, defended him, telling reporters that Romney's tax rate is close to the 15 percent rate most Americans pay on long-term capital gains from the sale of investments.

Romney's advisers stressed that he met all his federal tax obligations, provided maximum transparency and did not take advantage of what they described as "aggressive" strategies often used by the ultra-rich. Still, for millions of taxpayers grappling with their own returns as tax season looms, Romney's multimillion dollar wealth provides a window into an unfamiliar world.

His 2010 return shows a number of foreign investments, including funds in Ireland, Switzerland, Germany and Luxembourg. Most of Romney's vast fortune is held in a blind trust that he doesn't control. A portion is held in a retirement account.

Romney's advisers acknowledged Tuesday that Romney and his wife, Ann, had a bank account in Switzerland as part of her trust. The account was worth $3 million and was held in the United Bank of Switzerland, said R. Bradford Malt, a Boston lawyer who makes investments for the Romneys and oversees their blind trust, which was set up to avoid any conflicts of interest in investments during his run for the presidency.

In 2009, UBS admitted assisting U.S. citizens in evading taxes and agreed to pay a $780 million penalty as part of a deferred prosecution agreement with the Justice Department.

The political discussion over releasing Romney's tax information highlighted an argument that Democrats are already starting to use against him — that he is out of touch with normal Americans. And it may well have hurt him in the South Carolina primary, where he lost by 12 percentage points to Gingrich after spending several days resisting calls to release the returns.

Asked during a round of television interviews about Romney's relatively modest tax rate, Obama adviser David Plouffe said: "We need to change our tax system. We need to change our tax code so that everybody is doing their fair share." Obama planned to talk about economic fairness in his State of the Union speech to Congress Tuesday night.

Other Democratic Party voices were less restrained. "He used every loophole in the book available to the wealthy and corporations to avoid paying his fair share," said Democratic National Committee Executive Director Patrick Gaspard.

On the other hand, Romney's wife, Ann, had told supporters at a Florida rally on Sunday: "I want to remind you where we know our riches are. Our riches are with our families."